E3010

Only labelled arguments can have default value.

Erroneous example

pub fn greet(name : String = "World") -> Unit {
  //                       ^ Error: Only labelled arguments can have default value.
  println("Hello, " + name + "!")
}

Suggestion

Use an optional argument with ? if you want to provide a default value:

///|
pub fn greet(name? : String = "World") -> Unit {
  println("Hello, " + name + "!")
}

Or remove the default value if you want to keep it as a positional argument:

///|
pub fn greet_without_default(name : String) -> Unit {
  println("Hello, " + name + "!")
}